At least three different methods are known for lining metal electrolytic cell covers that are suitable for use in the amalgam process:
The application of a non-detachable rubber covering or lining to a conventional steel cover or internally lining the cover with non-detachable titanium sheets.
In addition plastics sheets may also be used to cover the cells (so-called "membrane covers").
The disadvantage of rubberised covers is that dioxin-containing and furan-containing reaction products can form on rubberised covers as the result of reaction with chlorine. A further disadvantage is the complicated and expensive maintenance of such covers. If a rubberised cover is to be relined, the rubber covering must first of all be brought to a state of brittle fracture, for example by subjecting it to cold, following which the rubber residues adhering to the cover have to be chiselled off.
Titanium-lined cell covers have the following disadvantages. The lining of steel covers with titanium sheets is fairly complicated and costly on account of the numerous welds on the anode ducts in the cell cover. Even if the titanium lining is only slightly damaged moist chlorine can come into contact with the cell cover, resulting in serious corrosion of the steel part. A proper skilled repair welding on the titanium lining is not possible on account of the deficient gas saturation of the gap between the titanium lining and corroded steel cover.
The replacement of a steel cover by a "membrane cover" of plastic material is very costly and difficult to implement in practice, since among other things the construction has to be altered for the current conduction. Besides, membrane covers have the disadvantage that they restrict the possibility of adjusting the anodes vertically.